Steam irons commonly have a soleplate comprising a metal casting having insert-molded heating elements extending through the casting, typically along a generally U-shaped path parallel to the bottom of the soleplate. A portion of the top the soleplate is covered by a sheet metal lid to form a steam chamber. The steam chamber is typically divided into a vaporization section, a blast path, and a steam vent section. The steam vent section may be divided into two or more subsections which may or may not be in open communication with one another. The vaporization section is located within the area between the legs of the U-shaped path of the heating element. Steam is produced during the normal course of operation by water dripped into the vaporization section onto a heated, upwardly-facing surface of the soleplate. The water is heated as it flows along the upper surface of the soleplate and converted into steam. The steam thus produced exits from the vaporization section into the steam vent sections through tortuous steam channels formed by surfaces included in the design of the soleplate. Plural steam outlet vents in the steam vent section permit steam to exit from the bottom of the soleplate onto the fabric or other material being pressed by the steam iron.
The steam blast path is located directly above, or almost directly above, an elongate portion of the heating element. Steam created along the blast path usually enters the steam vent sections through the same tortuous channels, or a portion of such channels, along which steam formed in the vaporization section passes.
A pair of ribs, namely an outer rib and an inner rib define the sides of a blast path. The ribs are ordinarily covered and sealed by the steam chamber lid. If the seal between the outer rib of the blast path and the chamber lid fail, water or water vapor from the blast path could escape the blast path and enter directly into the steam vent section. As result, water could exit the steam vent and cause undesirable "trailing" of streaks of water on the material being pressed. Trailing can also occur if water which has not been entirely vaporized into steam, either in the vaporization section or along the blast path, is permitted to enter the steam vent sections through the steam channels which are intended to direct only steam into the steam vent sections.